Plasmonic Au Nanoparticles Research Articles

Three-dimensional ZnO@TiO2 core-shell nanostructures decorated with plasmonic Au nanoparticles for promoting photoelectrochemical water splitting

A novel three-dimensional (3D) core-shell nanostructure decorated with plasmonic Au nanoparticles (NPs) was prepared for photoelectrochemical water splitting. In the new nanostructure, ZnO nanorods (NRs) are perpendicular to ZnO nanosheets (NSs), and the ZnO NSs-NRs are coated with a thin TiO2 shell formed by liquid phase deposition. The plasmonic Au NPs were formed in situ on the surface of ZnO NSs-NRs@TiO2 by thermal reduction. A thin TiO2 shell and uniformly distributed Au NPs were successfully obtained. The photoconversion efficiency and photocurrent density of the 3D ZnO NSs-NRs@TiO2-Au nanostructure respectively reached 0.48% and 1.73 mA cm−2 at 1.23 V vs. reversible hydrogen electrode, 4.80 and 4.33 times higher than those of ZnO NSs, respectively. The thin TiO2 shell effectively promoted charge separation, while the surface plasmon resonance effects of the Au NPs improved the photocurrent density. The findings suggest that the 3D ZnO NSs-NRs@TiO2-Au nanostructure is a promising photoanode for photoelectrochemical water splitting.

Incorporating plasmonic Au-nanoparticles into three-dimensionally ordered macroporous perovskite frameworks for efficient photocatalytic CO2 reduction

Recently, halide perovskite nanocrystals have drawn great attention in photocatalytic CO2 reduction due to their suitable band alignment and outstanding optical-response capability. However, the intrinsic carrier recombination and the poor mass transport still hinder the practical photocatalytic CO2 reduction performance of halide perovskites. Herein, a novel three-dimensionally ordered macroporous Au-CsPbBr3 (3DOM Au-CPB) composite is demonstrated and applied as a high-efficient visible-light-driven CO2 reduction photocatalyst. Owing to the rationally designed 3DOM structure, better light-harvesting has been achieved. The loading of Au nanoparticles on one hand further enhances the optical response performance of the photocatalyst with the surface plasmon resonance effect; on the other hand, better carrier separation performance is realized by the band bending effect at the Au/CPB interfaces. Due to the synergy effect, the 3DOM Au-CPB catalyst offers greatly enhanced photocatalytic CO2 reduction activity compared with bulk CPB. This work provides a new approach to design novel metal/halide perovskite photocatalysts, which can be further applied in designing other halide perovskite-related devices.

Plasmonic Au Nanoparticle Arrays for Monitoring Photopolymerization at the Nanoscale

The localized surface plasmon resonance (LSPR) of Au nanoparticles (NPs) was used to monitor photopolymerization at the nanoscale by in situ monitoring the optical response of AuNPs during the light-induced polymerization process. To show the interest of this approach, two configurations were used, which correspond to a resonant and a nonresonant excitation regime between the photopolymer and the AuNPs used as nanoprobes. We show that not only this method enables the progress monitoring of the photopolymerization reaction at the nanometric scale but also can highlight the near-field coupling effect responsible for the acceleration of the photoinduced reaction. This methodology appears very interesting to study the photoinduced nanofabrication processes of metal/polymer hybrid nanoparticles and more globally to study the photopolymerization reactions at the nanometric scale.

Synergistic photo/electrocatalysis for energy conversion and storage

Synergistic photo/electrocatalysis for energy conversion and storage

Enhancement of Scattering and Near Field of TiO2-Au Nanohybrids Using a Silver Resonator for Efficient Plasmonic Photocatalysis.

Recently, localized surface plasmon resonances (SPRs) of metallic nanoparticles (NPs) have been widely used to construct plasmonic nanohybrids for heterogeneous photocatalysis. For example, the combination of plasmonic Au NPs and TiO2 provides pure TiO2 visible-light activity. The SPR effect induces an electric field and consequently enhances light scattering and absorption, favoring the transfer of photon energy to hot carriers for catalytic reactions. Numerous approaches have been dedicated to the improvement of SPR absorption in photocatalysts. Here, we have designed a core@shell-satellite nanohybrid catalyst whereby an Ag NP core, as a plasmonic resonator featuring unique dual functions of strong scattering and near-field enhancement, is encapsulated by SiO2 and TiO2 layers in sequence, with Au NPs on the outer surface, Ag@SiO2@TiO2-Au, for efficient plasmonic photocatalysis. By varying the size and number of Ag NP cores, the Au SPR can be tailored over the visible and near-infrared spectral region to reabsorb the scattered photons. In the presence of the Ag core, the incident light is efficiently confined in the reaction suspension by undergoing multiple scattering, thus leading to an increase of the optical path to the photocatalysis. Moreover, using numerical analysis and experimental verifications, we demonstrate that the Ag core also induces a strong near-field enhancement at the Au-TiO2 interface via SPR coupling with Au. Consequently, the activity of the TiO2-Au plasmonic photocatalyst is significantly enhanced, resulting in a high H2 production rate under visible light. Thus, the design of a single structural unit with strong scattering and field enhancement, induced by a plasmonic resonator, is a highly effective strategy to boost photocatalytic activity.

Visible Light-Induced Reactivity of Plasmonic Gold Nanoparticles Incorporated into TiO2 Matrix towards 2-Chloroethyl Ethyl Sulfide

Inexpensive strategies for efficient decontamination of hazardous chemicals are required. In this study, the effect of visible light (λ > 400 nm) on the decomposition of 2-chloroethyl ethyl sulfide (2-CEES, a sulfur mustard (HD) simulant) on Au/TiO2 photocatalyst under anaerobic and aerobic conditions has been investigated in situ by diffuse reflectance infrared Fourier –transformed spectroscopy (DRIFTS). Under anaerobic conditions, 2-CEES partially desorbs from the Au/TiO2 surface likely due to the photothermal effect, induced by photo-excited plasmonic Au nanoparticles. In the aerobic experiment, no visible light effect is observed. We attribute this behavior to 2-CEES consumption by hydrolysis to 2-ethylthio ethanol in the dark, prior to visible light excitation. Oxygen activates water molecules in the dark, resulting in accelerated 2-CEES hydrolysis.

Plasmonic Anti‐counterfeiting Labels Based on the Au@SiO2‐Embedded Electrospun Fibers

AbstractA new type of plasmonic anti‐counterfeiting labels is designed on the basis of Au@SiO2 core–shell nanoparticles (Au@SiO2 NPs) and electrospun fibers. The fingerprint information of Raman active molecules is amplified by the plasmonic Au nanoparticles, and silica layers endow the stability of encoding information. Electrospun fibers with unordered breathable structure play the role of polymer matrix and own the flexible features. Au@SiO2 NPs are first adsorbed on the surface of poly(methyl methacrylate)/poly(4‐vinylpyridine) (PMMA/P4VP) fibers by noncovalent interactions, and then are decorated in/on the fibers by controlling the temperature. That is, when the temperature is higher than the glass transition temperature (Tg) of polymer matrix, partial Au@SiO2 NPs are embedded in the PMMA/P4VP fibers. The composite fibers based on the Au@SiO2 and PMMA/P4VP fibers are fabricated, and the signals of Raman active molecules are amplified in the Au@SiO2/PMMA/P4VP fibers. The peak positions and intensity of spectra from surface‐enhanced Raman spectroscopy are transferred into plasmonic anti‐counterfeiting labels with different spaces and widths. The anti‐counterfeiting labels are further encrypted into quick response (QR) codes and decrypted by the smartphone. The QR codes are difficult to copy and easy to authenticate, and composite fibers possess superior stability and show potential application in the field of anti‐counterfeiting.

Yolk-Shelled Gold@Cuprous Oxide Nanostructures with Hot Carriers Boosting Photocatalytic Performance.

Plasmonic Au nanoparticles (NPs) have been commonly used to enhance the photocatalytic activity of Cu2O. Till now, core-shell Au NP@Cu2O composites have been reported in previous studies. Yet, these Au@Cu2O composites only exhibit visible light response. Other special Au nanostructures, such as Au nanorods (NRs) or Au nanobipyramids (NBPs), which possess near-infrared light absorption, were rarely used to endow the near-infrared light response for Cu2O. In this work, for the first time, we used Au NPs, Au NRs, and Au NBPs and employed a handy and universal method to synthesize a series of yolk-shelled Au@Cu2O composites. The results showed that the yolk-shelled Au@Cu2O composites had much higher photocatalytic activity than their solid-shelled ones and pure Cu2O. More importantly, yolk-shelled Au NR@Cu2O and Au NBP@Cu2O composites indeed presented excellent near-infrared light-driven photocatalytic activity, which were impossible for Au NP@Cu2O and pure Cu2O. This outstanding performance for yolk-shelled Au NR@Cu2O and Au NBP@Cu2O could be attributed to the transfer of abundant hot electrons from Au NRs or Au NBPs to Cu2O, and the timely utilization of hot holes on Au through the rich pore channels on their yolk-shelled structure. Furthermore, yolk-shelled Au@Cu2O also showed better stability than pure Cu2O, owing to the migration of the oxidizing holes from Cu2O to Au driven by the built-in electric field. This work may give a guide to fabricate controllable and effective photocatalysts based on plasmonic metals and semiconductors with full solar light-driven photocatalytic activities in the future.

Vertical 3D Printed Forest‐Inspired Hierarchical Plasmonic Superstructure for Photocatalysis

AbstractEfficient light‐harvesting is of significant importance to achieve high solar energy utilization efficiency for various solar‐driven technologies. Compared with a 2D planar structure, a 3D plasmonic structure can largely increase the light adsorption/interaction areas and also utilizes the plasmonic effect to achieve much higher light utilization efficiency. However, this remains challenging in terms of structural design, reliable manufacturing, and ability to scale up. Herein, inspired by the light absorption strategy of natural forests, a hierarchical plasmonic superstructure is demonstrated composed of vertical TiO2 pillar arrays (as tree trunks), dense nanorod arrays (as branches), and a large number of plasmonic Au nanoparticles (as leaves). Such a forest‐like plasmonic superstructure can effectively absorb light from the surface plasmonic resonance effects of Au nanoparticles and the multiple scattering of light in the hierarchical branched structure. The strong light absorption and abundant photocatalytic active sites help yield a 15‐fold higher nitrogen photo‐fixation activity than that of the flat TiO2 films decorated with Au nanoparticles. The study provides an effective strategy to construct 3D plasmonic superstructures with excellent light‐harvesting efficiency and high stability and can be readily applied to a range of light‐driven applications

Reaction pathway change on plasmonic Au nanoparticles studied by surface-enhanced Raman spectroscopy

Gold nanoparticles (Au NPs) are nanoscale sources of light and electrons, which are highly relevant for their extensive applications in the field of photocatalysis. Although a number of research works have been carried out on chemical reactions accelerated by the energetic hot electrons/holes, the possibility of reaction pathway change on the plasmonic Au surfaces has not been reported so far. In this proof-of-concept study, we find that Au NPs change the reaction pathway in photooxidation of alkyne under visible light irradiation. This reaction produces benzil (COCO) without the presence of Au NPs. In contrast, as indicated by surface-enhanced Raman spectroscopic (SERS) results, the CC triple bonds (CC) adsorbed on Au NPs are converted into carboxyl (COOH) and acyl chloride (COCl) groups. The plasmonic Au NPs not only provide energetic charge carriers but also activate the reactant molecules as conventional heterogeneous catalysts. This study discloses the second role of plasmonic NPs in photocatalysis and bridges the gap between plasmon-driven and conventional heterogeneous catalysis.

Enhanced photocatalytic activity of plasmonic Au nanoparticles incorporated MoS2 nanosheets for degradation of organic dyes

In the present paper, we have investigated the effect of plasmonic gold nanoparticles (Au NPs) decoration on the photocatalytic efficiency of molybdenum disulfide (MoS2) nanosheets. The Au NPs are grown on the surfaces of chemically exfoliated MoS2 nanosheets by chemical reduction method with four different concentrations. The resulting Au-MoS2 nanostructures (NSs) are then characterized by X-ray diffractometer, Raman spectrometer, absorption spectrophotometer, field emission scanning electron microscopy, energy dispersive X-ray, and transmission electron microscopy (TEM). Sizes of the exfoliated MoS2 nanosheets are ~ 700 nm. In addition, the sizes of Au nanoparticles increase from 8.02 ± 2.03 nm to 9.81 ± 3.18 nm with the increase in concentrations of Au ions, as revealed by TEM imaging. Exfoliated MoS2 and Au-MoS2 NSs are used to study the photocatalytic degradation of organic dyes, methyl red (MR) and methylene blue (MB). Under UV–Visible light irradiation, pristine MoS2 shows photodegradation efficiencies in the range of 30.0% to 46.9% for MR, and 23.3% to 44.0% for MB, with varying exposure times of 30 to 120 min. However, Au-MoS2 NSs with the sets having maximum Au NPs concentrations, show enhanced degradation efficiencies from 70.2 to 96.7% for MR, and from 65.2 to 94.3% for MB. The degradation rate constants vary from − 0.5660 to − 1.5551 min−1 for MR dye, and vary from − 0.3587 to − 1.2614 min−1 for MB dye. The multi-fold enhancements of degradation efficiencies for both the dyes with Au-MoS2 NSs, can be attributed to the presence of Au NPs acting as charge trapping sites in the NSs. We believe this type of study could provide a way to battle the ill-effects of environmental degradation that pose a major threat to humans as well as biodiversity. This study can be further extended to other semiconducting materials in conjugation with two dimensional materials for photocatalytic treatment of polluted water.

Coagulation-Inspired Direct Fibrinogen Assay Using Plasmonic Nanoparticles Functionalized with Red Blood Cell Membranes.

The fast measurement of fibrinogen is essential in evaluating life-threatening sepsis and cardiovascular diseases. Here, we aim to utilize biomimetic plasmonic Au nanoparticles using red blood cell membranes (RBCM-AuNPs) and demonstrate nanoscale coagulation-inspired fibrinogen detection via cross-linking between RBCM-AuNPs. The proposed biomimetic RBCM-AuNPs are highly suitable for fibrinogen detection because hemagglutination, occurring in the presence of fibrinogen, induces a shift in the localized surface plasmon resonance of the NPs. Specifically, when the two ends of the fibrinogen protein are bound to receptors on separate RBCM-AuNPs, cross-linking of the RBCM-AuNPs occurs, yielding a corresponding plasmon shift within 10 min. This coagulation-inspired fibrinogen detection method, with a low sample volume, high selectivity, and high speed, could facilitate the diagnosis of sepsis and cardiovascular diseases.

Tuning interlayer spacing of MoS2 for enhanced hydrogen evolution reaction

The MoS2 structure engineering including hybrid structure construction and material self-optimization (edge sites improvement and phase transition), is a potential solution to boost photocatalytic hydrogen evolution reaction (HER) performance. Among the influence factors to MoS2 structure, the interlayer distance, which is a significant and non-ignorable parameter, plays a momentous role in tuning the photoelectric property and photocatalytic activity of MoS2. Here, we prepare MoS2 with different interlayer distances, and explore the corresponding optical and electrical properties. As the MoS2 interlayer spacing expands, the MoS2-1.12 (interlayer spacing 1.12 nm) is equipped with optimal light absorption ability, broadened energy band structure, high carrier mobility, and good electron transfer performance, compared to the MoS2-0.87 (interlayer spacing 0.87 nm) and MoS2-0.62 (interlayer spacing 0.62 nm). Consequently, the sample MoS2-1.12 possesses better HER performance (hydrogen production rate 311.28 μmol/g/h) than the MoS2-0.87 and MoS2-0.62. In addition, the MoS2 @Au core-shell structure with optimal interlayer distance is designed to further enhance the HER ability, and the H2 production rate of the MoS2-1.12@Au (773.4 μmol/g/h) is 2.48 times than that of the MoS2-1.12. The remarkable enhancement originates from the additional plasmonic Au nanoparticles. These results are significant for developing promising MoS2-based photocatalysts in the field of photocatalytic HER.

Role of plasmonic Au nanoparticles embedded in the diamond-like carbon overlayer in the performance of CuFeO2 solar photocathodes

Role of plasmonic Au nanoparticles embedded in the diamond-like carbon overlayer in the performance of CuFeO2 solar photocathodes

Enhancing photoelectrochemical water splitting with plasmonic Au nanoparticles.

The water-based renewable chemical energy cycle has attracted interest due to its role in replacing existing non-renewable resources and alleviating environmental issues. Utilizing the semi-infinite solar energy source is the most appropriate way to sustain such a water-based energy cycle by producing and feeding hydrogen and oxygen. For production, an efficient photoelectrode is required to effectively perform the photoelectrochemical water splitting reaction. For this purpose, appropriately engineered nanostructures can be introduced into the photoelectrode to enhance light–matter interactions for efficient generation and transport of charges and activation of surface chemical reactions. Plasmon enhanced photoelectrochemical water splitting, whose performance can potentially exceed classical efficiency limits, is of great importance in this respect. Plasmonic gold nanoparticles are widely accepted nanomaterials for such applications because they possess high chemical stability, efficiently absorb visible light unlike many inorganic oxides, and enhance light–matter interactions with localized plasmon relaxation processes. However, our understanding of the physical phenomena behind these particles is still not complete. This review paper focuses on understanding the interfacial phenomena between gold nanoparticles and semiconductors and provides a summary and perspective of recent studies on plasmon enhanced photoelectrochemical water splitting using gold nanoparticles.

Synergistic promotion of photoelectrochemical water splitting efficiency of TiO2 nanorod arrays by doping and surface modification

In the present work, we employed N-doping as well as surface modification with plasmonic Au nanoparticles (NPs) for synergistic promotion of PEC efficiency of TiO2 nanorod arrays.

Ultraviolet light-emitting diode-assisted highly sensitive room temperature NO2 gas sensors based on low-temperature solution-processed ZnO/TiO2 nanorods decorated with plasmonic Au nanoparticles.

Nanostructured semiconducting metal oxides such as SnO2, ZnO, TiO2, and CuO have been widely used to fabricate high performance gas sensors. To improve the sensitivity and stability of gas sensors, we developed NO2 gas sensors composed of ZnO/TiO2 core-shell nanorods (NRs) decorated with Au nanoparticles (NPs) synthesized via a simple low-temperature aqueous solution process, operated under ultraviolet irradiation to realize room temperature operation. The fabricated gas sensor with a 10 nm-thick TiO2 shell layer shows 9 times higher gas sensitivity and faster response and recovery times than ZnO NR-based gas sensors. This high performance of the fabricated gas sensor can be ascribed to band bending between the ZnO and TiO2 core-shell layers and the localized surface plasmon resonance effect of Au NPs with a sufficient Debye length of the TiO2 shell layer.

The design of magneto-plasmonic nanostructures formed by magnetic Prussian Blue-type nanocrystals decorated with Au nanoparticles.

We have developed a general protocol for the preparation of hybrid nanostructures formed by nanoparticles (NPs) of molecule-based magnets based on Prussian Blue Analogues (PBAs) decorated with plasmonic Au NPs of different shapes. By adjusting the pH, Au NPs can be attached preferentially along the edges of the PBA or randomly on the surface. The protocol allows tuning the plasmonic properties of the hybrids in the whole visible spectrum.

High-performance, self-powered UV photodetector based on Au nanoparticles decorated ZnO/CuI heterostructure

Self-powered Ultraviolet (UV) photodetectors (PDs) have attracted great attention due to their outstanding performance. Herein, we report the successful fabrication of self-powered UV PDs based on ZnO/CuI/Au heterojunction. An ultra-high on/off ratio of 4250 and fast rise/decay times of 0.41/0.08 s have been demonstrated from the ZnO/CuI/Au PD. Moreover, the PD exhibits a high responsivity of 61.5 mA/W and detectivity of 1.7 × 1010 Jones. The device displays long-term cyclic stability with 98.9% retention after 1000 cycles continuous test and superior environmental stability with 97.1% retention tested after 6 months. The synergistic effects of plasmonic Au nanoparticles and ZnO/CuI pn heterostructure play important roles in the enhancement of the photodetect ability. The concept of employing plasmonic Au nanoparticles onto the heterostructure indicates huge potential in achieving self-powered UV PDs for practical applications.

Optical Properties and Excited-State Dynamics of Atomically Precise Gold Nanoclusters.

Understanding the excited-state dynamics of nanomaterials is essential to their applications in photoenergy storage and conversion. This review summarizes recent progress in the excited-state dynamics of atomically precise gold (Au) nanoclusters (NCs). We first discuss the electronic structure and typical relaxation pathways of Au NCs from subpicoseconds to microseconds. Unlike plasmonic Au nanoparticles, in which collective electron excitation dominates, Au NCs show single-electron transitions and molecule-like exciton dynamics. The size-, shape-, structure-, and composition-dependent dynamics in Au NCs are further discussed in detail. For small-sized Au NCs, strong quantum confinement effects give rise to relaxation dynamics that is significantly dependent on atomic packing, shape, and heteroatom doping. For relatively larger-sized Au NCs, strong size dependence can be observed in exciton and electron dynamics. We also discuss the origin of coherent oscillations and their roles in excited-state relaxation. Finally, we provide our perspective on future directions in this area.